As is well known in the art, treatment of various medical conditions commonly involves implantation of medical devices and/or insertion of medical instruments into a body. Illustrative is the implantation or deployment of heart valves to regulate the flow of blood through cardiovascular vessels, and pacemakers to control abnormal heart rhythms.
Implantable medical devices; particularly, cardiovascular implants, have unique blood biocompatibility requirements to ensure that the device is not rejected (as in the case of natural tissue materials for heart valves and grafts for heart transplants) or that adverse thrombogenic (clotting) or hemodynamic (blood flow) responses are avoided.
Several cardiovascular implants, such as heart valves, are formed from natural tissue. Illustrative are the heart valves disclosed in U.S. Pat. Nos. 6,719,788 and 5,480,424 to Cox. The disclosed bioprostheses can, however, be affected by gradual calcification, which can, and in many instances will, lead to the eventual stiffening and tearing of the implant.
Many non-bioprosthetic implants are, however, fabricated from various metals and polymeric materials, and other exotic materials, such as pyrolytic carbon-coated graphite.
For example, pacemakers, defibrillators, leads, and other similar cardiovascular implants are often fabricated from Ni—Co—Cr alloy, Co—Cr—Mo alloy, titanium, and Ti-6Al-4V alloy, stainless steel, and various biocompatible polymeric materials. Artificial heart valves are often fabricated from various combinations of nylon, silicone, titanium, Teflon™, polyacetal, graphite and pyrolytic carbon.
Artificial hearts and ventricular assist devices are often fabricated from various combinations of stainless steel, cobalt alloy, titanium, Ti-6Al-4V alloy, carbon fiber reinforced composites, polyurethanes, Biolon™, Hemothane™, Dacron™, polysulfone, and other thermoplastics.
Finally, catheters and guide wires are often fabricated from Co—Ni or stainless steel wire. In many instances, the wire is encased in a polymeric material.
As is well known in the art, several major problems are often encountered when a medical device (or other device, e.g., tracking apparatus) fabricated from one of the aforementioned materials is implanted in the body. A major problem that is often encountered after implantation of such a device in the body is inflammation of surrounding tissue.
Another major problem is the high incidence of infection.
A further problem that is often encountered after implantation of the medical device in the body is the formation of blood clots (thrombogenesis).
One additional problem that is also often encountered is the degradation, e.g., corrosion, of medical device leads and, thereby, premature failure of the device after implantation in the body.
Most medical devices are designed to be implanted in the body for an extended period of time. However, when a harsh biological response (or premature failure of the device) is encountered after implantation, it is often necessary to remove the device through a secondary surgical procedure, which can, and in many instances will, result in undesirable pain and discomfort to the patient, and possibly additional trauma to the adjacent tissue. In addition to the pain and discomfort, the patient must be subjected to an additional time consuming and complicated surgical procedure with the attendant risks of surgery.
There is thus a need to provide medical devices that are configured for implantation in the body, and substantially reduce or eliminate the harsh biological responses associated with conventional implanted medical devices, including inflammation, infection and thrombogenesis.
It is therefore an object of the present invention to provide sheet structures for encasement structures that are configured to encase a medical device therein and that substantially reduce or eliminate the harsh biological responses associated with conventional implanted medical devices, including inflammation, infection and thrombogenesis, when implanted in the body.
It is another object of the present invention to provide sheet structures for ECM encasement structures that are configured to encase a medical device therein, and effectively improve biological functions and/or promote modulated healing of adjacent tissue and the growth of new tissue when implanted in the body.